internal notes notifications are sent in cleartext
a lot of work was done to redact outgoing mail notifications for confidential issues and notes on confidential issues (#23 (closed)).
but there's one corner case we do not seem to have a way to handle right now, and it's "internal notes". that's a comment made on a public issue (internal notes on confidential issues are fine, because the issue is confidential) with the Make this an internal note
flag.
Those do not seem to have any header our filter can act on. It does have the magic header, but it's set to false, e.g.:
X-GitLab-ConfidentialIssue: false
@micah is that a use case you had in mind?